1. Field of the Invention
This invention relates generally to resilient plastic straps and buckles and more particularly to such straps and buckles which are formed as a single, unitary piece in which the strap is also self-interlocking.
2. Description of the Prior Art
Means for imparting mechanical stength and flexibility to a plastic strap or belt has already been described in U.S. Pat. No. 2,445,889. According to the patent cited, straps formed of thermoplastic material follow only slowly and gradually an applied force or the removal of such a force and have limited mechanical strength. To provide a resiliency or spring action in the longitudinal direction in such straps as well as to reinforce them, a thin strip of spring metal is completely embedded in each strap. The spring metal is sandwiched between two strips of thermoplastic which is consolidated into a single strap by heat treatment or by cementing. In the event the spring metal becomes exposed, it can seriously injure the wearer; the hazard is particularly great when the wearer is exposed to severe impact forces. Hence such straps are not suitable for use in protective devices for athletes engaged in contact sports.
Further, the straight outer side edges of the straps in the patent cited, while useful in preventing the tearing of the strap and exposure of the metal strip, conform poorly to the contour of an object about which the strap is placed. In applications in which the strap is stretched across the muscle of a wearer's limb, such a strap tends to chafe the wearer's skin or to cut into protective foam padding placed beneath the strap.
Moreover, the transversely-extending, elongated apertures in the patent cited occupy only a minimal portion of the surface area of each strap, the apertures being limited to the central portions of each strap in which the metal strip is not embedded. The amount of ventilation to reduce perspiration caused by the strap is also minimal, further adding to the discomfort experienced by wearers of such a strap.